I am going to start developing my own Game Engine for ActionScript 3.0 - Is there anybody out there who's already made one, and is willing to share the resources they used to learn the best practices etc?

Here is a link to a 2D Flash game engine. I've never used it and I really don't have a lot of experience with Flash game development, but from the examples they have on the features page it seems like a well developed engine. It might be a good starting point for you to expand off of or as a reference engine.

Some favourite quotes:

Spoiler

Never trust a computer you can't throw out a window.- Steve Wozniak

The best way to prepare [to be a programmer] is to write programs, and to study great programs that other people have written.- Bill Gates

There's always one more bug.- Lubarsky's Law of Cybernetic Entomology

Think? Why think! We have computers to do that for us.- Jean Rostand

Treat your password like your toothbrush. Don't let anybody else use it, and get a new one every six months.- Clifford Stoll

To err is human - and to blame it on a computer is even more so.- Robert Orben

Computing is not about computers any more. It is about living.- Nicholas Negroponte

Yes if the goal is just to make the next uber engine with no basis of a game behind it then sure, it's a valid response. However, generally people have some sort of idea in their head about what kinda game they're trying to make or what they would like to see their project do.

Even if its not a game, it still requires some sort of framework with all the necessary components to support whatever idea it is they have in their head. Renderer, scene management, loading of assets from disk. application state management, etc.. etc..

For me, what I'm working on is a terrain "engine" (I use that term very loosely) that supports paging terrain assets in and out of memory based on distance from the player. I've mostly worked out how Im going to do the management of all that and have most of the frame work up and running. I have no current plans of making a game out of this as this would require more time than I as a single person can contribute, for now... Eventually that may change once I've gotten this project to a certain point and its functional.

If you'd like, I could say I'm making a game where the goal is the player has a rock that they're pushing around the terrain to try and drop it in a hole in the ground. It doesn't really change the required framework of code needed to achieve the above.

I hear the message in the article and the whole "make a game, not an engine" thing, i really do. It makes sense from the standpoint of senselessly creating an engine that just supports random features that the game may or may not use. Yes, that is wasted time, lacking in direction and just firing aimlessly in the dark. But I don't think that 90% of the people that ask this type of question, not have some sort of game in mind when they ask it. I'm sure they have a vision, it's likely what drove them to be interested in programming in the first place.

game engines tend to be genre specific. IE shooter engine, 2d scroller engine etc. An engine that makes angry birds type games would be useless when making an f-22 flight simulator.

so, first question: what type(s) of games do you want your engine to be able to do?

you should start by implementing one gametype to start. once you have that, you can add capabilities to do other game types.

and you should have a "target game" in mind. the same way you have a "target player" or "target user" in mind when you make a game. IE who's your customer?

recent postings on this topic have caused me to revisit the "game engine" idea. if there was a silver bullet engine that could be built, i sure could use it, as i have more work to do than i have time for (imagine being an indie with about half a dozen titles to maintain).

but recent contemplation of the question has again led to the conclusion that genre specific or one-off engines are the way to go.

an alternative to the engine approach is the library/template. here, instead of a program the user plugs data into, you have libraries and boilerplate code the user uses to build the program. This approach is much more flexible. One can pick and choose the components used: lets see, i'm doing an F22 sim, i'll use the skybox and ground systems from the library, but don't need the pathfinding. i'll use the library's physics engine as it already supports 3 degrees of rotational freedom (which most shooter engines don't). and so on... this way the code that belongs in the game is in the game, and the code that belongs in the library is in the library, with a minimum of callbacks.

so the first step is to come up with a target game. what kind of game your engine should do (first). this will define the genre or category of games it can do. it will also define the component list (i need ground drawing, skybox, movement & collision, etc.). then you decide whether to do an app or a lib. as i said, libs are more flexible. but with an app, you can sit a non-programmer down and they can build a game. that's the basic tradeoff. coders can do anything code related. non-coders con only do what can be done with tools made by coders for non-coders. So in that respect, you need to identify your target user, as well as the type of target game they'd be making. so the question becomes: who's my customer? a programmer, or a non-programmer? and what kind of game are they making? this will determine lib vs app, and game type supported.

once you've decided on lib vs app and gametype, then its very similar to building a game, but you spend time on the "engine" instead of on content and such.

Meh, I think that graph in wintertime's link nails the idea down very succinctly.

The thing with me is, I am staying away from making a multi-function, general purpose game engine and just doing something that fulfills one core aspect (graphics), but that in itself can still be general purpose. Right now I plan to halt my "main" engine progress to work on two games, one big and one small. The big game will be longer term but in the meantime I still want to produce smaller games that take less time.

My smaller, as of yet not started, game will take code from what I have made in my graphics engine and re-purpose and trim it in size to only keep what I need for the game. So it's going to be sort of a "lite" version of the engine. I still prefer each domain of logic as separate as possible and only have some wrappers as helper code with which to tie certain aspects together, like making a game object that needs both a graphical and physics representation.